The present invention relates to integrated circuit (IC) packaging, and more particularly to a lead frame for an integrated circuit device having both J-leads and Gull Wing leads.
FIG. 1 is a side view of a portion of a semiconductor device 10 comprising a plastic body 12 that houses one or more integrated circuits, and a plurality of leads projecting from a side thereof, where two such leads 14 and 16 are shown. The plastic body 12 protects the integrated circuit, while the leads 14 and 16 allow for external electrical connection to the integrated circuit. In order to allow adjacent leads to be located close together (i.e., to reduce lead pitch), and therefore have more leads spaced around the body 12, some of the leads, like the lead 14, are bent outward, and other ones of the leads are bent inward, like lead 16. The outward bending leads are known as Gull Wing leads and the inward bending leads are known as J-leads. It also should be noted that the Gull Wing leads 14 project from the side of the package body 12 at a different plane than the J-leads 16.
FIG. 2 is a cross-sectional side view of the package 10 prior to bending of the leads 14 and 16. It can be seen that the package 10 includes a flag 20 and an integrated circuit die 22 attached to a surface of the flag 20. The die 22 is electrically connected to the leads 14 and 16 with bond wires 24. There also is a tape 26 placed on an upper surface of the leads 14 and 16 to keep adjacent leads spaced from each other.
FIG. 3 is a top plan view of a lead frame 30 used to assemble the integrated circuit device 10 of FIGS. 1 and 2. The lead frame 30 comprises the generally rectangular die pad 20 surrounded by the leads 14 and 16. As noted above, adjacent leads 14 and 16 are very close to one another. To prevent adjacent leads from bending or coming into contacting with one another, the tape 26 is placed over the leads to hold them in place.
FIG. 4 illustrates formation of one of the J-leads 16 during a molding process in which the plastic body 12 is formed. In the upper half of the drawing, the lead 16 is shown prior to insertion into a mold, and in the lower half of the drawing, the lead 16 is shown interacting with mold tooling 40 and 42. The lead 16 has an inner lead side that is proximate to the die pad 20, and an outer lead side that is distant from the die pad 20. The dashed line A-A indicates the boundary of the package body 12, separating the inner and outer lead sides of the lead 16. The tape 26 is placed over the inner lead side to keep adjacent leads separated from each other. As shown in the lower half of FIG. 4, a portion 40 of the mold tooling presses down on the outer lead side of the lead 16, close to the inner lead side, while a distal end of the outer lead portion of the lead 16 is clamped with another portion 42 of the mold tooling. The mold tooling 40 and 42 offsets adjacent leads at the package body, so that the Gull Wing leads 14 and the J-leads 16 are vertically offset where they project from the package body 12, as shown in FIGS. 1 and 2.
Unfortunately, this pressing and lead deformation can cause the tape 26 to separate from the leads 16, as shown in the lower half of FIG. 4, where the tape is above the lead 16 because the lead 16 was pressed down by the mold tooling 40. Accordingly, a minimum lead pitch requirement may be violated or worse yet, one of the Gull Wing leads 14 may contact an adjacent J-lead 16, causing an electrical short circuit. Accordingly, it would be advantageous to have a lead frame and/or a method of preventing such a rule violation or short circuit condition.